Observation of Initial Procalcitonin and the Clinical Course of Patients With Acute Respiratory Tract Infections

Primary endpoint: * initial Procalcitonin values of patients with Acute Respiratory Tract Infections Secondary endpoints: * correlation of initial Procalcitonin values to classify Acute Respiratory Tract Infections * correlation of initial Procalcitonin values to subjective severity of Acute Respiratory Tract Infections * correlation of initial Procalcitonin values to antibiotic- prescriptions * correlation of initial Procalcitonin values to frequency of admission to hospital * correlation of initial Procalcitonin values to frequency of referrals (radiology, pneumology)